You’ve heard us mention time and time again that your smile is often the first thing people notice about you. And in the pursuit of a perfect smile, many often turn to hydrogen peroxide. But is it safe to use? We asked the experts.

“Using peroxide diluted appropriately can certainly help maintain gum tissue health and can slowly whiten teeth,” says New York cosmetic dentist Jason Kasarsky, DDS. It kills bacteria and even has the power to help heal mouth sores and disinfect your toothbrush. But the key thing to remember is that you have to use it properly and dilute it to a safe percentage.

“While a diluted concentration of hydrogen peroxide is marketed and sold professionally over the counter as an oral rinse, there are some concerns with its use,” says Fort Washington, PA, prosthodontist Glenn J. Wolfinger, DMD. “The major problem arises in patient's ability to accurately dilute solutions and monitor usage to a safe level.”

Dr. Kasarsky says to follow the “one third, one third and one third” rule. That means that the mixture you use should include equal parts of hydrogen peroxide, water and Listerine. If you feel unsure of your mixing ability, you can use a product called Peroxyl that contains a safe amount of hydrogen peroxide.

“There are no bad effects that can occur if you dilute it appropriately,” says Dr. Kasarsky. If it’s not diluted properly, you can create tooth sensitivity and blanche your gums, although the negative effects typically don’t last very long. As for the rumor that rinsing with hydrogen peroxide can cause cancer, that’s a myth as it’s not a known carcinogen.